The present invention relates to contrast enhanced portable message signs using LED arrays in a cabinet.
Portable changeable light emitting diode (xe2x80x9cLEDxe2x80x9d) message signs, such as those manufactured by American Signal Company and by Precision Solar Controls, Inc., (e.g., their Solar Message Center 2000 product), are typically manufactured with a transparent front surface (commonly made of LEXAN(copyright) or other transparent or translucent material) that is tilted downwards in order to reduce the reflection from oncoming headlights bouncing back into the eyes of an automobile driver. In the conventional manufacturing process, the front of the sign is tilted down approximately 5 degrees while the back surface remains vertical thus causing the top surface to be wider than the bottom surface (see FIG. 1). The printed wiring boards are mounted parallel to the vertical back surface with the LED""s mounted normal to the plane of the printed wiring boards, causing the center of the cone of light thus emitted to be aimed towards the horizon. Automatic equipment for installing LED""s in printed wiring boards, such as a 6348 Radial Inserter available from Universal Instruments Corporation, is designed to only mount the LED""s normal to the plane of the printed wiring board. LED""s are mounted to the board either as through-mounts or surface-mounts.
The front and back surfaces being anti-parallel can cause problems in manufacturing; e.g., alignment of the angled portion with the array, spacing to prevent rattling, additional material may be required, and the like. Additionally, the front surface typically has a black screen printed on it with selected clear areas through which the LED illumination shines. With conventional tilted signs, the clear areas at the top of the sign must be larger in diameter than those at the bottom of the sign because at the top the front surface is farther away from the LED array than at the bottom. This can lead to inefficient presentation of the illumination array. Also, this can reduce the apparent half power angle of the LEDs in the array.
It would be desirable to have a contrast enhanced, more easily manufactured sign enclosure and mounting assembly that would present a downward tilted front surface to reduce headlight reflection yet maximize illumination power detectable by the oncoming driver. Such a product would enable the LED to be aimed at the horizon to provide the greatest illuminating power to the oncoming driver, yet have a downward tilted front surface to reduce headlight or sunlight reflection.
The present invention comprises a message sign having an angled front surface to reduce reflection of light from oncoming lights. The sign includes a printed circuit board having light emitting devices mounted thereto at an angle with respect to the board so that when the board is mounted in the sign and parallel to the front surface, the light emitting devices are angled generally parallel to the horizon so as to optimize the amount of light being emitted and visible to an oncoming driver. A number of variations of angling mechanisms and techniques are presented.
In one embodiment an LED is provided having two pins of different lengths. When the pins are mounted to or through the board, the pin length differential causes the LED to be angled with respect to the board.
In another embodiment, conventional through mount LED""s are positioned in the board and a plate having apertures corresponding to the geometric layout of the LED""s in the board is placed over the LED""s. The plate can be moved parallel to the board causing the LED pins to bend and the LED""s to be angled with respect to the board.
In a further embodiment, the board has a series of raised lines of epoxy or other material associated therewith so that when the LED""s are positioned over the board, a portion of the LED is positioned over the raised line and the LED is thus tilted. Alternatively, the raised lines can be raised dots proximate to the place on the board where each LED is to be mounted. In another alternative embodiment, the dots can be positioned in different places with respect to the LED so that different LED""s can be tilted at different angles. In this manner a xe2x80x9cwide anglexe2x80x9d light emitting device is created, thus increasing the viewing angle of light beyond currently available single LED half power angles.
In yet a further embodiment, surface mounted LED""s are mounted on two different height surfaces associated with the board to provide an angled LED.
In still another embodiment, The LED""s, either through mount or surface mount, could be mounted on narrow strips of printed circuit board material, for example one half inch wide by 12 inches long. The strips would then be mounted at an angle, for example of 5 degrees, to point towards the horizon.
Other features and advantages of the present invention will become apparent upon reading the following detailed description of embodiments of the invention, when taken in conjunction with the appended claims.